Endoscopes are frequently used in a medical setting for diagnostic and therapeutic procedures. Borescopes, their industrial counterpart, are frequently used in industrial settings for internal inspection of machines and manufactured parts. Endoscopes and borescopes are sometimes manufactured with one or more working channels through the scope for passing instrumentation through for performing diagnostic or therapeutic procedures within the field of view of the scope. The working channel in an endoscope is also sometimes referred to as the biopsy channel of the scope. It is common to use an inner liner within the working channel of endoscopes and borescopes. Sometimes, the inner liner is a single-use, disposable item. The inner liner provides a low friction surface to facilitate passage of instruments and helps to avoid damage to the interior of the scope by the instruments as they pass through the working channel. The inner liner also helps to avoid contamination of the interior of the scope by the instruments as they pass through the working channel. This is especially important in medical applications where the small diameter working channels may be difficult to clean and sterilize between uses. A sterile, disposable inner liner can be used to keep the working channel of the endoscope clean. For rigid endoscopes and borescopes, which typically use rod optics for image transfer through the scope, the working channel can be lined with a simple thin-walled tube without concern for the flexibility of the liner. However, for flexible endoscopes and borescopes, which use flexible fiberoptics for image transfer through the scope, the inner liner for the working channel must be sufficiently flexible to bend with the scope without kinking or collapsing, which would compromise the inner lumen of the working channel. Flexible endoscopes and borescopes may be made flexible along their entire length or they may be made with a flexible distal section and a relatively rigid proximal section. It is important that the flexible portion of the working channel liner be at least as long as the flexible section of the scope for which it is intended. The present invention provides an improved flexible inner liner for the working channel of flexible endoscopes and borescopes. For the sake of brevity, endoscopes and borescopes will both be referred to as endoscopes in the following detailed description of the invention. However, it should be kept in mind that, except where specifically stated to the contrary, the description and the accompanying comments apply equally well to medical endoscopes and to industrial borescopes.
Another technical area relevant to the present invention involves catheters. The term "catheter" embraces a wide variety of elongated, generally tubular, devices for insertion into a body lumen or cavity for diagnostic or therapeutic purposes. These include inter alia cardiovascular catheters, urology catheters, visceral catheters and catheter introducers. Catheters can be introduced into the body through the working channel of an endoscope or they can be introduced independently under endoscopic, fluoroscopic or ultrasonic guidance. The construction of the disposable flexible inner liner of the present invention will also be beneficial for the construction of many varieties of catheters.